(1) Field of the Invention
This invention relates to a flame-retardant styrene-base resin composition having well-balanced specific gravity, impact resistance and heat resistance and flame retardancy. Specifically, it relates to an improved flame-retardant styrene-base resin composition which contains both halogenous flame retardant and antimony compound and can successfully meet the requirements prescribed in the UL Standard, 94V-2.
(2) Description of the Prior Art
Styrene-base resins have already been used for various applications such as household electric appliances and office automation equipment owing to their superb moldability and processability, mechanical properties, electrical properties and the like. Reflecting the increasing enactment of various regulations for flame retardation in recent years typified by the UL Standard, flame-retarded styrene-base resins have also been developed and brought into use. Among such flame-retarded styrene-base resins, flame-retardant styrene-base resin compositions which meet the requirements of the UL Standard, 94V-2 are used in video tape recorders, audio systems and the like, all of which enjoy outstanding growth rates recently, and their consumption is hence increasing rapidly. Accordingly, there is an outstanding demand for the development of a flame-retardant styrene-base resin composition which has well-balanced specific gravity, impact resistance and heat resistance and flame retardancy.
As a method for imparting flame retardancy to a styrene-base resin, it has conventionally been known to make combined use of a flame retardant such as halogen compound or phosphorus compound and a flame-retarding additive such as antimony compound. Where flame retardancy is imparted especially by using a halogen compound and an antimony compound, their synergistic effects are believed to reach the maximum when the weight ratio of halogen atoms/antimony atoms is 3. Flame retardancy, which meets the requirements of the UL Standard, 94V-2, is believed to be imparted in a similar manner. This method has thus been used widely.
In a resin which contains halogen atoms and antimony atoms at a weight ratio of 3 and meets the requirements of the UL Standard, 94V-2, the flame retardancy of the resin is ensured. In order to achieve such flame retardancy, it is however indispensable to increase the total amount of the halogen compound and antimony compound relative to the resin. As a result, the resin has a high specific gravity and inferior impact resistance and heat resistance. Its specific gravity and above-mentioned properties are therefore not satisfactorily balanced with its flame retardancy. The resin is by no means satisfactory as a molding material.